This had to be number one on my carol list. This song is on the short list of gospel songs that always have the power to make me cry. Unlike many of the other Christmas carols listed, the song is well suited for instrumental and vocal power/energy, and Enya has that in spades. Most of the sounds on the song are her voice being layered out, and if she needs an instrument, she's playing it. It's powerful in English, and just as powerful in the original Latin.